The surge of the Green party has emphasised an iron rule of British politics: those on the left cannot be treated as legitimate political actors. A case in point came at the weekend, when the Green party leader, Zack Polanski, was interviewed by Sky News’ Trevor Phillips, who barely concealed his contempt.

Two weeks ago, in an interview with Haaretz newspaper, Polanski was asked what the Green party’s response was to the recent wave of attacks against Jewish sites in the UK. His response: “I’m concerned about rising antisemitic attacks. We saw arson attacks on ambulances, for instance, and we know that, increasingly, Jewish communities are feeling unsafe. Now, there’s a conversation to be had about whether it’s a perception of unsafety or whether it’s actual unsafety, but neither are acceptable.”

Phillips misrepresented Polanski’s comments, twisting his remarks into a claim that the threats to his community were imaginary. What Polanski actually said was that he feels that – at times – pro-Palestine marches have been perceived as unsafe by some Jewish people and safe by others, including himself.

Polanski then asked a question presumably already on the minds of many viewers: “Why is my Jewish identity being erased from this conversation?” Phillips’ reply was extraordinary: “Don’t try that one on me!” Try what, exactly? Phillips continued to push the point that “many” Jewish people felt differently to Polanski, without attempting to understand the point of view of the Jewish man sitting in front of him. He studiously ignored Polanski’s references to his own experiences of antisemitism, one incident leading to two men being arrested and another involving the disruption of a Green party rally in Hastings by rightwing activists, during which Nazi salutes were performed. He also failed to engage when Polanski raised the issue of a cartoon in the Times that depicted him with a grotesquely hooked nose – one of the most recognisable antisemitic tropes.

Surely if a Jewish Labour or Tory leader had been spoken to like this, there would have been national outrage. But Polanski is both Jewish and left wing – and therefore, it would appear, not a legitimate political figure whose identity should be respected or listened to.

It wasn’t just Phillips; other journalists responded in the same way. “For Polanski, ‘Jew’ is his political shield,” wrote Times columnist Janice Turner last week. On the Sky News panel that followed the Trevor Phillips interview, another Times columnist, Melanie Phillips, who is herself Jewish, accused Polanski of being a “menace to public safety” and went on to describe him as “using his Jewish ancestry as a shield to protect him from what he’s doing”. Her reasoning here? “He is repeating the canard that Israel is committing a genocide.”

Presumably this logic extends to pre-eminent Jewish Israeli genocide scholars such as Omer Bartov, who has written: “I have been teaching classes on genocide for a quarter of a century. I can recognise one when I see one.”

There is something else at work, too, with these attacks on Polanski’s politics. There is a delegitimising of the Palestinian rights that he seeks to stand up for. Melanie Phillips has previously claimed that “If you support the Palestinian Arab cause today, you are facilitating deranged and murderous Jew-hatred.” At an event last year she declared: “There is no such thing as the Palestinian people … the Jews are the only people who have any entitlement to any of this land.” And if that left room for doubt, she added: “And they are the only people who have an entitlement to all of it.”

There is a lesson here about British political discourse. Say almost anything about Palestinians, however inflammatory, and your career will remain intact. Oppose their destruction, and you will be vilified.

The day after he monstered Polanski, Trevor Phillips appeared on Times Radio. He said that there is “an Islamist community that wants to kill Jews and they want to use the arguments that are being had about the Middle East as cover for their malign intent”. He said the Green party “draws its support from that community”, fearing that if it “does the right thing and comes out clearly against Jew hate it will find itself on the wrong side of that Islamist minority and its supporters in that community”.

Taken on their own terms, his points are ridiculous. Why would Islamists so fanatical that they want to kill Jews vote for a secular party led by a gay Jewish man, with the most socially progressive platform of any political party? How do his comments square with the Green party’s repeated, explicit condemnations of antisemitism?

To be clear, there have been allegations of vile antisemitism expressed by Green party candidates who have since been suspended. There have been a small number of examples in a party that has nearly quadrupled in size, to almost 230,000 members, since September last year. To extrapolate from these cases and smear an entire party rooted in anti-racism, as the Daily Mail has done today, is cynical.

But Trevor Phillips will never have to answer these questions. He can continue to present himself as an impartial broadcaster because his bias runs in a direction that remains acceptable. Those on the left, after all, are not regarded as legitimate political actors – and so anything goes.

• Owen Jones is a Guardian columnist

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